Sounds: Quality Vs. Size

Sounds: Quality Vs. Size

Changing the compression on his photographs shrunk Bryan's presentations to a size he could distribute more easily. But before he sent them out, he decided to see what else we could optimize. The next thing we looked at was his sound files.

Just as with photographs, optimizing sound files involves finding a balance between quality and file size. If you have super-high quality sounds in the presentation, the size of the files will reflect that. How high the quality of the sound files needs to be depends to some extent on will be used for sounds. Voice-overs and narration can be lower quality, while music should be of a higher quality. In addition, look at whether you really need to use 16-bit stereo sounds for a presentation that will only be played through a computer's speakers .

In general, sound quality and effects such as volume and fades will have to be adjusted outside of PowerPoint. PowerPoint MVP Geetesh Bajaj's Indezine has a great page ( with up-to-date information on a wide variety of sound editors in a wide variety of price ranges, from free on up.

If using PowerPoint 2002 or later, you have a volume setting on the Sound Setting tab of the Custom Animation Effect Options for the sound. You can't use the volume setting for all sound types, only those which don't get volume control from your computer's system volume control.

Can't use it for these types

Can use it for these types

CD Audio
















No matter what version of PowerPoint you use, you can adjust the quality of the sounds from within PowerPoint when recording narration. To record narration, go to Slide Show Record Narration. The resulting window allows you to start narrating.

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Figure 11-3: Record Narration Window

Before starting narrations , adjust the quality of the sound files by clicking the Change Quality button.

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Figure 11-4: Sound Selection Window

Click the drop down for Name ; there are three default sound setups: CD Quality, Radio Quality and Telephone Quality. Select each in turn and notice the changes in the Attributes box.

The default choice for recording is CD quality, 44KHz at 16-bit stereo. This will take the most space at 172KB per second of sound. You will need only 46 KB per second if you change to 48KHz at 8-bit mono. The change from stereo to mono won't be noticeable in most situations and the higher sampling rate should help cover the quality differences.

Radio quality reduces the sound quality and records in mono, taking only 21KB per second of sound. Telephone quality is very low quality sound, but takes virtually no space at 10KB per second. However, telephone quality is often the most appropriate choice for voice narration. It will sound good enough, without taking too much space.

Once sound quality is selected, click OK and return to the Record Narration window. Click OK to start the presentation and record the narration. In addition, PowerPoint will note where in the narration the slide transitions and other clicks occur.

If you don't want the narrations embedded in the PowerPoint presentation, click the checkbox for Link narrations in, set the path for the files to the same folder as the presentation and off you go. Why wouldn't you want them embedded? Because if the files aren't embedded, you can edit them in a sound editor to correct mistakes. Since the sound files will be recorded as WAV files, you can reembed them later.

The best way to determine what quality of sound needed for a given presentation is to record some narration at each of the three default settings. Play the narration back through a couple of different speaker sets and listen.

By testing his sound levels, Bryan learned two things:

  • First, none of the branch employees would be listening to the presentation on high quality speakers, so using radio quality was more than good enough for the product catalog. This cut the size of his sounds to less than 20% of the size he had originally used. While he could have re-recorded the sounds to get the savings, instead he used a sound editor to reduce the quality (and size) of the sound files.

  • Second, he discovered the desktop computers used by some of the managers didn't have speakers at all. So, when he distributed the CD, he had to include a note that the product catalog included sounds and needed to be played on a system with external speakers.

Linking Vs. Embedding

If embedding all the graphics, sounds and other objects, the file size may be quite large. This is not unusual. You can shrink the size of the PowerPoint file by linking these files instead of embedding them. This won't necessarily shrink the overall space required for the presentation, since the extra files must be included when distributing the presentation.

If sound or graphic files are linked, be sure to put the linked files in the same folder as the presentation before linking to them and keep them with the presentation when distributing it.

Kathy Jacobs On PowerPoint
Kathy Jacobs On PowerPoint
ISBN: 972425861
Year: 2003
Pages: 166 © 2008-2017.
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